Variable A/C Supply for the Workbench
This project was inspired by the need for a variable A/C supply with current limiting and overload protection for use on the test
bench when working with old A/C powered equipment or prototyping A/C powered circuits. It uses several old school parts and ideas
that have been very useful over the years. This project just packages everything in a nice enclosure that lives on the workbench.
The project is build in a recycled 3U 19" shallow rack case from some old radio equiment. The project starts with a 10 amp circuit breaker
that protects the entire box. This feeds an industry standard stop/start station feeding a relay to provide an emergency stop feature and also
provides for a feature where the panel will stay de-energized after a power failure. A standard fixed voltage A/C duplex receptacle is available
(protected by 10A breaker and stop/start switching) for auxillary equipment such as a soldering iron. The switched A/C feed then goes to a
variac (variable auto transformer), a 100W light bulb that is used as a visable current limiting device, a pair of output meters and the
output socket. The current limiting light bulb may be switched in or out of the circuit as desired. A 5A circuit breaker protects the variable
output side of the panel.
Finished Power Supply
The front panel is a piece of laser engraved arborite glued to some 3mm baltic birch plywood. This gives a very durable and nice looking panel.
Laser Engraved Arborite Panel